Four people hurt when an explosion ripped through a Pennsylvania nursing home two weeks ago sued the facility and a natural gas utility on Monday, claiming their negligence was to blame.

Two workers at Bristol Health & Rehab Center LLC, a resident of the suburban Philadelphia facility and a contractor who happened to be there when the blast occurred on Dec. 23 filed the lawsuit. The defendants include PECO Energy Company, which provided natural gas to the complex, its parent company Exelon Corp., and Saber Healthcare Holdings LLC of Beachwood, Ohio.

The lawsuit filed in Philadelphia court claims the defendants “were aware of a gas leak in the building and failed to take the steps necessary to evacuate the building, fix the leak and protect the residents, workers and others that were exposed to the horrific blast.”

Zach Shamberg, Saber Healthcare Group chief of government affairs, said in an email Monday that the company is cooperating with the ongoing investigation and does not comment on litigation.

PECO communications director Greg Smore said in an email that as a party to an investigation by the National Transportation Safety Board, the company was not permitted to comment. The gas utility has previously said the cause is under investigation and it’s not known whether PECO’s equipment or natural gas were involved.

The explosion killed a resident and a worker and injured 20 other people. Officials have not said what caused it, but a PECO crew had been there to investigate a reported gas leak.

The lawsuit claims the gas leak “had been festering for days” and the gas odor came from the boiler room.

“Defendants' decision not to immediately initiate evacuation procedures under these circumstances was reckless and outrageous given the population within the building, with many of the residents having limited mobility and unable to self-evacuate in the case of an emergency,” the lawsuit alleged.

A utility crew was responding to reports of a gas odor when the explosion happened, authorities have said.

Authorities reported acts of heroism in response to the explosion. About 100 residents were taken to other nursing homes nearby, officials said.

One of the people who died was Muthoni Nduthu, 52, a Kenyan immigrant who worked there. The other victim was a resident whose name has not been made public.

The force of the blast shook nearby houses for blocks in Bristol, about 20 miles (32 kilometers) northeast of Philadelphia.